From: Jiang Liu <jiang.liu@huawei.com>
To: Christoph Lameter <cl@linux.com>
Cc: Jiang Liu <liuj97@gmail.com>, Pekka Enberg <penberg@kernel.org>,
Matt Mackall <mpm@selenic.com>, Mel Gorman <mgorman@suse.de>,
Yinghai Lu <yinghai@kernel.org>, Tony Luck <tony.luck@intel.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
David Rientjes <rientjes@google.com>,
Minchan Kim <minchan@kernel.org>,
Keping Chen <chenkeping@huawei.com>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 2/4] mm: make consistent use of PG_slab flag
Date: Fri, 6 Jul 2012 16:30:20 +0800 [thread overview]
Message-ID: <4FF6A21C.9010509@huawei.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1207051236310.8670@router.home>
On 2012-7-6 1:37, Christoph Lameter wrote:
>> Hi Chris,
>> I think there's a little difference with SLUB and SLOB for compound page.
>> For SLOB, it relies on the page allocator to allocate compound page to fulfill
>> request bigger than one page. For SLUB, it relies on the page allocator if the
>> request is bigger than two pages. So SLUB may allocate a 2-pages compound page
>> to host SLUB managed objects.
>> My proposal may be summarized as below:
>> 1) PG_slab flag marks a memory object is allocated from slab allocator.
>> 2) PG_slabobject marks a (compound) page hosts SLUB/SLOB managed objects.
>> 3) Only set PG_slab/PG_slabobject on the head page of compound pages.
>> 4) For SLAB, PG_slabobject is redundant and so not used.
>>
>> A summary of proposed usage of PG_slab(S) and PG_slabobject(O) with
>> SLAB/SLUB/SLOB allocators as below:
>> pagesize SLAB SLUB SLOB
>> 1page S S,O S,O
>> 2page S S,O S
>>> =4page S S S
>
> There is no point of recognizing such objects because those will be
> kmalloc objects and they can only be freed in a subsystem specific way.
> There is no standard way to even figure out which subsystem allocated
> them. So for all practical purposes those are unrecoverable.
Hi Chris,
This patch is not for hotplug, but is to fix some issues in current
kernel, such as:
1) make show_mem() on ARM and unicore32 report consistent information
no matter which slab allocator is used.
2) make /proc/kpagecount and /proc/kpageflags return accurate information.
3) Get rid of risks in mm/memory_failure.c and arch/ia64/kernel/mca_drv.c
Thanks!
next prev parent reply other threads:[~2012-07-06 9:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-03 3:57 [RFC PATCH 1/4] mm: introduce a safer interface to check whether a page is managed by SLxB Jiang Liu
2012-07-03 3:57 ` [RFC PATCH 2/4] mm: make consistent use of PG_slab flag Jiang Liu
2012-07-05 14:47 ` Christoph Lameter
2012-07-05 16:15 ` Jiang Liu
2012-07-05 17:37 ` Christoph Lameter
2012-07-06 8:30 ` Jiang Liu [this message]
2012-07-06 13:53 ` Christoph Lameter
2012-07-03 3:57 ` [RFC PATCH 3/4] SLAB: minor code cleanup Jiang Liu
2012-07-03 3:57 ` [RFC PATCH 4/4] mm: change slob's struct page definition to accomodate struct page changes Jiang Liu
2012-07-05 14:45 ` [RFC PATCH 1/4] mm: introduce a safer interface to check whether a page is managed by SLxB Christoph Lameter
2012-07-05 15:55 ` Jiang Liu
2012-07-05 17:36 ` Christoph Lameter
2012-07-06 7:29 ` Jiang Liu
2012-07-06 13:50 ` Christoph Lameter
2012-07-06 15:36 ` Jiang Liu
2012-09-04 9:18 ` Wen Congyang
2012-09-04 12:13 ` Jiang Liu
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